include<stdio.h>
include
include
using namespace std;
int main()
{
long int L,N,list[600];
while(scanf("%d %d",&L,&N)!=EOF)
{
for(int i=0;i<N;i++)
{
scanf("%d",&list[i]);
}
sort(list,list+N,greater<int>());
int sum=0;
for(int i=0;i<N;i++)
{
if(L>0)
{
L-=list[i];
sum++;
}
else break;
}
if(L>0)
{
printf("impossible\n");
}
else
{
printf("%d\n",sum);
}</int>
} return 0;
}